The invention generally relates to a cartridge for a metal air battery.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a sheet-like layer, typically called the separator.
When a battery is used as an electrical energy source in a device, such as a cellular telephone, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In a metal air electrochemical cell, oxygen is reduced at the cathode, and a metal is oxidized at the anode. Oxygen is supplied to the cathode from the atmospheric air external to the cell through one or several air access port(s) in the container.
In a prismatic metal-air electrochemical cell, a cartridge is typically used a battery housing. The cartridge allows air to reach the cathode to drive the electrochemical reactions. The cartridge also keeps the cathode electrically isolated from the anode, which can sometimes leak from the cell.
The invention generally relates to a battery cartridge that provides good protection against leakage of battery material. The cartridge can be used with batteries used in devices such as cellular telephones.
In one aspect, the invention features a battery including a cartridge having a first casing having a wall; and a second casing having an outer wall having a height, and an inner wall having a height less than the height of the outer wall, wherein the walls of the second casing are spaced for receiving the wall of the first casing. Preferably, the wall of the first casing extends entirely around the periphery of the first casing. In addition, the outer wall of the second casing extends entirely around the periphery of the second casing, and/or the inner wall of the second casing extends entirely around the second casing. With such a cartridge, a simple, two-piece design is provided. This design helps to minimize cost of production and simplifies the manufacturing and assembling process.
The first casing can include an area recessed from an interior surface of the first casing such that a cathode can be disposed on the interior surface of the casing. An absorbent layer can be disposed within the recessed area of the casing. By placing the absorbent layer into the recessed area, the cathode can be directly sealed to the casing. The direct seal between the cathode and the casing reduces the chance of leakage at this point. In addition, this allows the cathode to lie more flatly which increases the internal volume of the battery.
The battery also includes at least one seal between the first casing and the second casing. The seal can be located between an end of the wall of the first casing and the second casing. For example, the end of the wall of the first casing can have a projection. This projection can be ultrasonically welded to form a seal between the wall of the first casing and the second casing. A seal can further be located between the outer wall of the second casing and the wall of the first casing. The seal can be an adhesive, e.g., an epoxy-potting compound. The battery further includes a cathode disposed in the first casing. When the casings are assembled together, the cathode is compressed against an end of the inner wall of the second casing. The battery can include a seal disposed between the end of the inner wall of the second casing and the cathode. Preferably, the battery has all three seals, thereby providing good protection against leakage of the battery material.
By assembling the battery such that the cathode is compressed against the inner wall of the second casing, the internal volume of the battery is increased. This provides for more space for anode material which results in increased capacity of the battery. The cartridge also requires no hot melt for sealing and eliminates use of a grid.
In another aspect, the invention features a method of assembling a battery. The method provides a simple manufacturing and assembly process. The method includes placing a cathode in a first casing having a wall; placing an anode material in a second casing having an outer wall having a height, and an inner wall spaced from the outer wall and having a height less than the height of the outer wall; and sealing the first casing and the second casing together such that the wall of the first casing is received between the walls of the second casing.
Sealing of the first casing and the second casing together can be performed by compressing the casings such that the cathode is compressed against an end of the inner wall of the second casing. A sealant can be placed on the end of the wall such that a seal is formed at the periphery of the cathode. The method can further include sealing the first casing to the second casing by forming a seal between the end of the wall of the first casing with the second casing. For example, the end of the wall of the first casing can have a projection, e.g., an energy director. This projection can be welded, e.g., by ultrasonic welding, to the second casing. Sealing of the first casing and the second casing can be performed by placing an adhesive, e.g., an epoxy compound, between the wall of the first casing and the outer wall of the second casing. Preferably, the method includes forming at least these three seals between the first casing and the second casing so that the chance of leakage from the battery is reduced.